(1) Field of the Invention
The present invention relates in general to an oil relief valve for internal combustion engines, and, more particularly, to such a valve which permits the escape of oil in an engine lubricant line when oil pressure rises.
(2) Description of the Prior Art
The use of oil relief valves are well known in lubrication systems for four-stroke cycle internal combustion engines in which the valve allows the escape of oil into an oil pan when internal oil pressure reaches a set level so as to maintain the system at constant pressure. When internal oil pressure is below the set level, the valve has its valve plug to rest on the valve seat sealing the port that is in communication with the oil pan. With the valve in this position, the oil or lubricant is allowed to circulate through the lubricant line between the oil pump and the various engine parts to be lubricated. When the oil pressure reaches the level, the valve plug lifts itself up from the seat to open the port bringing the line into communication with the oil pan. As a result, portion a of the lubricant is caused to escape into the oil pan and the internal pressure begins to drop. When the oil pressure drops to the level, the valve plug, which is normally urged toward the seat by the action of the spring, is forced down to close the port.
However, those conventional oil relief valves have proved to pose noise problems because of their very design. Each time the system pressure rises and reaches a set level, the valve plug pops up in quick response opening the port to permit the escape of oil into the oil pan, which follows an immediate pressure drop in the system. The increased force of the spring now compressed by the plug will react to this pressure drop and drives the plug down to the seat. With the closure of the port, the system again begins to increase pressure to the level. As a result, the plug is caused to move up again. In this way, the valve plug pops up and down in a rapid succession bringing about a vibration problem generally called "chattering", the rapidly repeated collision of a valve plug against its seat, with a resultant premature wear in the valve seat.
Examples of the prior art oil relief valves for internal combustion engines are disclosed in laid open Japanese patent applications 62-20655 and 58-137809.